ALUMINIUM. 213 



proceed to impress the fact, that the earth alumina bears the 

 same relation to the metal aluminium that rust of iron does 

 to the metal last named. 



Immense magazines or storehouses of the earth or rust 

 alumina are furnished in beds of clay ; nevertheless, he who 

 desires to procure alumina in moderate quantities may ob- 

 tain it far more readily from the crystalline material alum 

 than from clay. If alum be dissolved in water, and harts- 

 horn added, the alumina will fall down in a somewhat gela- 

 tinous form, because it is combined with water ; but on being 

 collected, washed, and heated, it assumes the characteristics 

 of a white powder, which sticks to the tongue just like a 

 piece of new tobacco-pipe. This white earth, alumina, is the 

 basis or stock material of all clays. Porcelain clay, which is 

 usually regarded as the type of purity for this class of bodies, 

 is made up of 60 parts alumina and 40 of silica in every 

 100 parts. 



There is yet another circumstance which conduces to a 

 similar result. Extremely minute quantities of materials are 

 often, in his researches, taken cognisance of by the chemist. 



For instance, when De Candolle tells us that gold is con- 

 tained in the roots of violets and in the stems and tendrils of 

 the vine, and copper in tobacco and coffee ; when Dr. Percy 

 tells us that silver exists in sea water ; and that every speci- 

 men of lead examined by him was found to be charged with 

 a portion of silver half the startling effeqt of such assertions 

 is lost to the mind, because of the confessedly minute portions 

 of the precious metals discoverable. It is with feelings of 

 real wonder, however, that a person listens to the statement 

 for the first time, that about fifty per cent of the pure matter 

 of clay consists of this strange metal aluminium. 



It is the fashion to speak of aluminium as a metal newly 

 discovered. This is a mistake. Aluminium was first obtained 

 by Sir H. Davy so long since as the year 1808 ; but he 

 obtained it in quantities so minute, that many of its leading 



